I had a similar problem going thru atleast three headlight bulbs in a short period of time.So I too tried different makes of bulbs,but no soap.So then I started to monitor my battery charge rate alittle more closely [via the instrument panel] and discovered that my battery was charging irratically.In other words, alittle high,then alittle low,and so forth,meaning it was fluctuating the voltage going thru the bikes' electrical system [instead of remaining fairly constant] which in turn will usually take out the weakest part of the system,or the head light bulb,in this case.So what you're looking for is a constant 14.2-14.6 charge rate showing on your voltmeter without frequently bouncing up and down. Anyways,after investigating my problem alittle further,I discovered that my battery ground cable,WHERE IT ATTACHES TO THE FRAME RAIL,[and this has been mentioned here] was, infact,also alittle on the loose side.So I tightened it alittle more [without breaking the bolt] and haven't had the problem since,not to mention,my charge rate now remains pretty steady,instead of fluctuating like it was. So this will be your starting point!!Good luck! Dave!!!